Integrated circuits have become a primary component in most of current electronic systems due to a low cost, high reliability, and speed. Fabrication of the integrated circuits begins with a substrate where each substrate is subjected to steps that form various circuit structures on the substrate. Typically, plasma (or, ionized gas) is used to perform process steps that include depositing material onto the surface of the substrate as well as removing and selectively etching patterns on the surface.
Typically, the plasma is formed above the surface of the substrate by adding energy to the process gas at low pressure. The resulting plasma may contain ions, free radicals, and neutral species with high kinetic energies. In plasma etching, the charged particles in the plasma can be directed to impinge upon the unmasked regions of the substrate and thereby remove atoms or molecules from the substrate.
Any non-uniformity of the plasma characteristics may cause uneven reaction rates along the surface of the substrate, which may decrease the manufacturing yield. As the substrate diameter tends to increase and transistor sizes formed on the substrate decrease, the non-uniformity has become one of the major complexities in plasma processing systems. Thus, there is a need for a plasma processing system that promotes plasma uniformity over the entire surface of the substrate.
Modern plasma etch tools use multiple knobs to control process parameters, such as plasma density and uniformity, chemical composition of plasma, ion energy and ion energy distribution near the substrate surface. New generation plasma processing systems require tighter control of these parameters in order to meet the requirements of technological challenges, such as shrinking feature size and new stack materials. As such, there is a need for an advanced plasma processing apparatus that allows a user to have an enhanced control of these parameters.